The present invention relates to a critical temperature sensitive resistor material of which the electric resistance changes greatly at a given temperature, and particularly relates to a thermally sensitive low hysteresis resistor material.
Thermally sensitive resistor materials include a critical temperature sensitive resistor material of which the electric resistance changes greatly at a given temperature. That is, a single crystal of VO.sub.2 or a sintered body of VO.sub.2 exhibits a resistance that changes by a factor of several thousand to several tens of thousands at a temperature of about 68.degree. C. It is said that the phenomenon of the great resistance change is attributed to the fact that VO.sub.2 undergoes a change in crystalline structure at a temperature of about 68.degree. C. between the monoclinic system (below 68.degree. C.) and the tetragonal system (above 68.degree. C.), and the fact that the electric conduction mechanism changes from electric conduction mechanism of semiconductor type of a high resistance into electri conduction mechanism of metallic type of a low resistance. Such a change in crystalline structure, i.e., a change which involves migration of atoms cause hysteresis in which change of resistance is delayed during the transient temperature conditions, and resistance characteristics are different between when the temperature rises from a low temperature to a high temperature and vice versa. At a certain temperature of about 68.degree. C., therefore, the resistor material exhibits two resistances that differ greatly. Usually, the temperature width of hysteresis is 2.degree. C. Therefore, the precision for detecting the temperature or for controlling the temperature is .+-.1.degree. C., which is not adequate for high-precision measurement.
Japanese Patent Publication No. 8547/1971 is quoted to show the state of the art.